Storage solutions

You get plastic storage bins and sheds that are for exactly the sort of situation you are in, Sonata. The most popular small one is shaped and sized like a small bench, you open up the lid and there are all your smaller tools etc.
There is a plotholder at my allotments site that has what is basically a very wide, shallow, walk in plastic wardrobe, specifically made for gardening equipment, comes with hooks and optional shelving...easily takes a small lawnmower, long handled hoes, etc, but needless to say not much shelter in a shower and not really a place to do potting on ! The drawback of course is the price, but they are good quality in my experience. Try Argos, or search for garden sheds online, the company I got my metal one from did all sorts of shapes and sizes.
Alternatively, you could do what all the locals in Braemar do when they want to make a cheapo stick shed for their firewood. Put in four upright posts, have the ones next to the wall higher than the ones further away; brace longitudinally and laterally with flat bits of stick, then cover the sides and top with whatever combination of plywood, roofing felt, tarpaulins and scaffold netting you have and want to use. As long as the posts are in securely, the braces are done right and you have something weighing the roof down at the edges, it is a really weatherproof setup. You can even put a gutter along the edge and run it into a water butt, as my father does. (His are deluxe models, roofing felt attached to ply for the roof, substantial sides.) With a wooden fence, assuming it is yours, the job is already half done for you, there are posts already in that you can nail onto etc. For a front/back door, I would be inclined to use a rollup flap of heavy duty polythene, something like a couple of fertiliser sacks stapled together and weighted at the bottom. And of course you can extend this idea as necessary, if the aspect is right you can create a nice wee shelter between sheds for a wormery, a sunwarmed waterbutt, a minigreenhouse...mm, I am gettin all sorts of ideas myself here !
Be warned, don't hang heavy things off the crosspieces, the roof will start to bow in the middle if you do.
Of course if you are unlucky your neighbours will hate this for what it does to their property values, but as it is a temporary wooden structure it is unlikely to fall within planning regulations.
Hope this helps.

You can get three foot wide sheds.

Bah, measured up and it's not quite 3 foot, so sounds like the storage cupboard thing is the way forward. We're not terribly handy or I'd be building a leanto like snohare suggests, sounds fab!

You'd be amazed how easy it is Sonata You should see the cockeyed, drunken staggered, hamfisted leantos there are in Braemar - and still they stay up, you can tell it is the easiest form of building known to (wo)man !
Whatever you do, I'd just like to thank you for your help on the issue of homelessness on behalf of the local spider population.

Hi Sonata, I think I've seen some narrow bike stores somewhere, but I don't know if they were that narrow - I'll do a bit of a search...

...darn it, Trimetals have one but its 35" externally!

Oh, what about this one...

Overlap Bike Store Garden Storage - Garden Sheds - BuyShedsDirect

scroll down for all the info.

I was lucky enough for my mum-in-law to give me her garden storage box which I use at home - it's invaluable for keeping all my bits and pieces in.
Argos have a good range of storage things - log onto the argos website - 705/6655 705/6631 705/1801 705/7087 705/2295
Maybe they could be of some use?

If you get a bike shed, don't forget to get one with sliding doors...

Have a look at specalist shed companys like southern sheds....get them to adapt you one.

Argos didn't have one in stock, but we managed to get one in B&Q. I put it together last night, cleared the side...and it's now all full of bits and bobs. It is rather small - only about 2' wide and more of a cupboard, but it fits down the side.

My 2 year old thought it was a "house" though and she loved it..now I have to block off the side to stop her trying to get in it!